This invention relates to a method for increasing the production of petroleum from subterranean formations containing heavy petroleum by use of fluid and electrical current conductive fractures in such formations.
Many oil-bearing formations are tight formations which do not permit the flow of oil from the formation into a wellbore at an acceptable rate.
When such formations are consolidated, fracturing with or without the use of proppants may be effective to increase the flow of petroleum from the formations. In some such formations, the petroleum is heavy and even when open fractures exist, the oil does not flow from the formation at an acceptable rate because of its high viscosity. Electrical heating of the formation in the vicinity of the wellbore has been used to increase the production of oil from such formations. In some instances, such electrical heating has been achieved by the use of electrically conductive proppants positioned in the fracture. Unfortunately, quantities of the proppant may be produced from the fracture with the viscous oil or redistributed in the fracture by the flow of the heavy oil from the formation. In such instances, both the electrical and the fluid conductivity of the fracture can be reduced or lost.
Other formations may be unconsolidated. Fracturing is less effective with such formations since the fractures tend to close when the fracturing pressure is removed. Proppants are less effective with such fractures since the proppant can become imbedded or enclosed by the unconsolidated formation either immediately or over time. It is desirable that methods be available to produce viscous oils from such formations. Conductive proppants and electrical heating have also been used in such formations in an attempt to increase the production of viscous oil. In such unconsolidated formations, sand or other unconsolidated material may also be produced with the oil. The proppant may be redistributed or lost or the fractures may be plugged by the migration of sand into the fracture containing the proppants during production of the viscous oil.
In both instances, both the fluid and the electrical conductivity of the proppant may be reduced or lost as a result of the redistribution or production of the proppant.
Accordingly, a continuing effort has been directed to the development of methods for positioning and maintaining a fluidly conductive and electrically conductive fracture in an oil-bearing formation.